NASA takes stick over feet and inches

NASA's insistence on sticking to pounds, feet and inches in its Constellation programme "could derail efforts to develop a globalised civilian space industry", New Scientistreports.

Leading the fight to bring NASA into the metric fold is Mike Gold of the US civilian space outfit Bigelow Aerospace. His company is "dedicated to developing next-generation crewed space complexes to revolutionize space commerce", and hopes that in the future the Constellation Orion capsule might carry paying customers to its orbiting outposts.

However, Gold fears possible imperial/metric incompatibility issues. He said: "We in the private sector are doing everything possible to create a global market with as much commonality and interoperability as possible. But NASA still can't make the jump to metric."

Carol Hockert, head of the weights and measures division at the US National Institute of Standards and Technology, weighed in behind Gold, telling New Scientist: "There are clear advantages to using metric units in terms of global commerce and international research collaborations. And space exploration certainly falls into a category that could benefit."

The problem is that NASA's Ares launch vehicle (see pic) - destined to lift Orion heavenwards - is a "shuttle-derived" design - based on 30-year-old specs and resolutely imperial.

NASA spokesman Grey Hautaluoma explained: "The shuttle and US segments of the ISS were built using the English system of measurements. And much of the Ares launch vehicle and Kennedy Space Center ground systems are legacy hardware built in the English system, too."

This old school approach is despite a 2004 agreement by NASA to "conform with US legislation enacted in 1988 that ordered all government departments to move towards the exclusive use of SI [International Standard] units".

The agency has proved reluctant to make the switch. In 2006, spokesman David Steitz told New Scientist: "NASA is in the process of converting to SI units. However, immediate conversion of systems that are already designed in English units can prove risky and inefficient. The US space program... will need time to evolve into SI units."

NASA is now citing budgetary constraints as the main reason for staying imperial. It's estimated that converting to SI units, including updating plans and software, would cost a whopping $370m - representing "almost half the cost of a 2009 shuttle launch", something which lightens US taxpayers' wallets by $759m.

Hautaluoma said: "We found the cost of converting to SI would exceed what we can afford."

He insisted: "Given these budget constraints and the need for consistent units throughout the Constellation Program lifecycle to minimise risks, and to contribute to mission success, we're revising the previous management directive to a primarily English-units-based program."

Gold is unimpressed with NASA's latest back-tracking. He bemoaned: "The space program is supposed to be about bridging barriers and bringing humanity closer together. Failing to adopt a globally accepted uniform system of measurement seems to fly in the face of that.

"Operating in space while using two different systems of measurement certainly opens the door for problematic mistakes and miscommunications."

Regarding "problematic mistakes", New Scientist reminds aficionados of metric/imperial cock-ups of the 1999 loss of the $125m Mars Climate Orbiter due to "the failed translation of English units into metric units in a segment of ground-based, navigation-related mission software".

This provoked "a major error in our understanding of the spacecraft's path as it approached Mars", as a NASA report subsequently put it. The result was that the Mars Climate Orbiter attempted to enter orbit way too low (60km, or 37 miles, if you're from NASA), and ended its mission in pieces on the surface. ®